JPH04279668A - Light diffusing resin - Google Patents

Abstract

PURPOSE:To obtain a composition suitable for lighting cover, having a fixed particle diameter distribution, small particle diameter, high light scattering properties and high light transmittance. CONSTITUTION:Fine particles of crosslinked polymer having 1-30mum average particle diameter and a standard deviation of particle diameter distribution of <=20% average diameter. The polymer has preferably 2-15mum average particle diameter, is spherical and is obtained by copolymerizing methyl methacrylate and/or styrene with a polyfunctional (meth)acrylate.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light-diffusing resin suitable for use in materials that require a light-diffusing function, such as various displays, illuminated signboards, transmission screens, and lighting covers.

0002

[Prior art and problems to be solved by the invention] Conventionally,
As a light-diffusing material used for lighting covers, screens, etc., materials in which organic or inorganic fine particles are dispersed in transparent plastic are known. As for the performance required of these materials, it is important to diffuse light uniformly and over as wide a range as possible. However, since the amount of light emitted from the light source is constant, the current situation is to optimize it by changing the concentration, particle size, etc. of the light diffusing material in order to obtain the most preferable brightness and spread. Furthermore, various materials have been proposed using the difference in refractive index between fine particles as a light diffusing material and resin as an index. However, there is no light-diffusing material that has sufficiently satisfactory light-diffusing properties for applications such as rear-projection television screens that require high scattering properties and light-diffusing base materials for electroluminescence (EL). Ta.

0003

[Means for Solving the Problems] Under these circumstances, the present inventors have made extensive studies to obtain an excellent light-diffusing material, and have found that the particle size distribution of fine particles dispersed in the resin influences the light-diffusing performance. This is an important factor, and the present invention was completed based on the discovery that if the particle size distribution is kept within a certain range, a light-diffusing resin that has excellent light-diffusing performance and is not colored by transmitted light can be obtained.

That is, the present invention provides a crosslinked polymer having an average particle size within the range of 1 to 30 μm and a standard deviation of the particle size distribution of 20% or less of the average particle size, in a substantially transparent resin. The present invention provides a light-diffusing resin in which fine particles are dispersed.

[0005] The average particle size of the crosslinked polymer fine particles used in the present invention is in the range of 1 to 30 μm, preferably 2 to 15 μm.
m range. If the average particle size is less than 1 μm, the transmitted light will be colored, which is undesirable, and if it exceeds 30 μm, the scattering intensity of the transmitted light will tend to decrease, causing problems.

In the present invention, it is necessary that the standard deviation of the particle size distribution of the crosslinked polymer fine particles be 20% or less of the average particle size, that is, the fine particles must be highly monodisperse. When the standard deviation exceeds 20%, that is, polydisperse fine particles cannot sufficiently satisfy both light scattering properties and light transmittance.

[0007] The shape of the crosslinked polymer fine particles is not particularly limited, but is preferably truly spherical. Note that the surface of the fine particles may be porous.

[0008] The crosslinked polymer fine particles having such an average particle size and particle size distribution within a certain range may be obtained by, for example, subjecting crosslinked polymer fine particles obtained using a suspension polymerization method to a classification treatment to make the particle size uniform. Alternatively, crosslinked polymer fine particles having a uniform particle size may be produced using a so-called seed polymerization method.

The polymer constituting the crosslinked polymer fine particles used in the present invention is not particularly limited, but styrene crosslinks such as styrene/divinylbenzene, styrene/ethylene glycol dimethacrylate, styrene/butadiene, etc. Copolymers; (meth)acrylate/divinylbenzene, methyl(meth)acrylate/ethylene glycol dimethacrylate, methyl(meth)acrylate/methylenebisacrylamide, etc.
Acrylic acid ester-based crosslinked copolymers; olefin-based crosslinked copolymers such as ethylene/butadiene, methyl vinyl ether/divinyloxybutane, vinyl acetate/divinyloxybutane, and vinyl chloride/divinylbenzene; In addition, when using methacrylic resin as a base,
Fine particles obtained by copolymerizing methyl methacrylate and/or styrene with a polyfunctional (meth)acrylate are preferably used. Here, the polyfunctional (meth)acrylates include (poly)ethylene glycol di(meth)acrylates such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, and tetraethylene glycol di(meth)acrylate; (meth)acrylate, 1,
Glycol di(meth)acrylates such as 3-butanediol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate; trimethylolpropane tri(
(Meth)acrylates of polyhydric alcohols such as meth)acrylate and pentaerythritol tetra(meth)acrylate are used.

The base resin of the light-diffusing resin needs to be a substantially transparent resin, and the higher the transparency (light transmittance), the more preferable it is. As such resins, methacrylic resins, epoxy resins, polycarbonate resins, polystyrene resins, polyvinyl chloride resins, etc. are used.

[0011] As a method for producing the light-diffusing resin of the present invention, for example, the above-mentioned crosslinked polymer fine particles are dispersed in syrup of a polymerizable monomer or a partially polymerized monomer and polymerized; Examples include a method of melt-kneading crosslinked polymer fine particles and a pre-prepared base resin and then pressing. Furthermore, when it is desired to form the light-diffusing resin into a thin film, a method such as screen printing can also be used.

The blending ratio of the crosslinked polymer fine particles in the light-diffusing resin is preferably 1 to 10% by weight. When the addition rate of fine particles is high, the amount of transmitted light decreases, which is not preferable. Further, if it is less than 1%, the effects of the present invention will not be sufficiently exhibited. When a methacrylic resin is used as a substrate, since the methacrylic resin usually has a refractive index of about 1.49, it is desirable that the refractive index of the crosslinked polymer fine particles is about 1.50 to 1.54.

[0013]

Effects of the Invention The light-diffusing resin of the present invention has a small particle size and a narrow particle size distribution, so it has both high light scattering properties and high light transmittance, and can be used in lighting covers, various displays, and lighting. It can be suitably used for signboards, etc.

[0014]

[Examples] The present invention will be explained in detail with reference to Examples below, but the present invention is not limited to these Examples. In addition, in the examples, parts indicate parts by weight, and % indicates weight %.

Example 1 To 1000 parts of a 3% aqueous solution of polyvinyl alcohol, 79 parts of methyl methacrylate (MMA), 19 parts of styrene,
2 parts of ethylene glycol dimethacrylate and 2,2-
Add a mixed solution of 1.0 part of azobisisobutyronitrile and finely disperse the mixture.
Polymerization was carried out for 5 hours. A further classification operation was performed to obtain crosslinked polymer fine particles having an average particle size of 6.3 μm and a standard deviation of 1.1 μm. The refractive index of this fine particle is JIS K
7105, the result was 1.514 as determined by measuring the movement of the Becke line using a microscope. An acrylic resin plate with a thickness of 1 mm was produced using the crosslinked polymer fine particles obtained above. That is, 91 parts of MMA, 9 parts of ethyl acrylate, and 0.1 parts of azobisisobutyronitrile.
The components were mixed and polymerized at 60° C. for 1 hour to obtain acrylic resin syrup. Add 1 part of the above fine particles to the syrup.
．． 5 parts were added and dispersed. Then, this was poured into a mold made of two glass plates equipped with a gasket, and after degassing, it was heated at 80° C. for 2 hours and then at 120° C. for 2 hours to perform polymerization. The plate thickness was adjusted to 1 mm to obtain a thin plate-like light-diffusing resin.

Examples 2 to 7 Except for controlling the particle size obtained by changing the stirring speed of the polymer dispersion when synthesizing crosslinked polymer fine particles,
Fine particles having different particle sizes were obtained by the same method as in Example 1. Using this, the light-diffusing resin shown in Table 1 was obtained in the same manner as in Example 1.

Comparative Examples 1 to 3 Fine particles were synthesized in the same manner as in Example 1, except that precision classification was not performed after polymerization. Using these fine particles, the light-diffusing resin shown in Table 1 was obtained in the same manner as in Example 1.

Test Example The light transmittance, light diffusing ability, and light diffusing properties of the light diffusing resins obtained in the above Examples and Comparative Examples were evaluated. [Method] (1) Light transmittance Light transmittance was evaluated by measuring total light transmittance using an integrating sphere type light transmittance measuring device. (2) Light diffusing ability Light diffusing ability is the ratio of the total light transmittance (Tt) and the diffuse transmittance (Td) of the light that enters the flat test piece from the rear and comes out in front, that is, Evaluation was performed by measuring the haze value. The haze value (H) was calculated using Equation 1.

(3) A 10 W fluorescent lamp was placed 10 cm behind the light-diffusing flat test piece, and visual observation was made from the front. ○: The outline of the fluorescent light cannot be seen. △: The outline of the fluorescent lamp is slightly visible.

[Table 1] [Results] As shown in Table 1, the light-diffusing resin of the present invention, in which the average particle size and particle size distribution of crosslinked polymer fine particles are within a certain range, has good light transmittance and light diffusivity. Both were good.

Claims (3)

[Claims] 1. Crosslinked polymer fine particles having an average particle size within the range of 1 to 30 μm and a standard deviation of particle size distribution of 20% or less of the average particle size are dispersed in a substantially transparent resin. A light-diffusing resin made by Seshite. 2. The light diffusion method according to claim 1, wherein the substantially transparent resin is a resin whose main component is at least one selected from methacrylic resins, polystyrene resins, polycarbonate resins, epoxy resins, and polyvinyl chloride resins. sex resin. 3. The light-diffusing resin according to claim 1, wherein the crosslinked polymer fine particles are a copolymer of methyl (meth)acrylate and/or styrene and a polyfunctional (meth)acrylate.